Preparing CSI using a set of zero amplitude parameters

ABSTRACT

Apparatuses, methods, and systems are disclosed for preparing channel state information (“CSI”). One apparatus includes a processor and a transceiver configured to communicate with a base unit over a RAN using spatial multiplexing, wherein multiple transmission layers are transmitted at a time, each transmission layer comprising multiple beams. The processor identifies a set of non-zero amplitude parameters and a set of zero amplitude parameters over the set of layers. The processor computes a number of non-zero amplitude parameters and determines an indication of the number of non-zero amplitude parameters. The processor determines the location of zero amplitude parameters to generate a set of location bits. The processor prepares CSI that includes the indication of the number of non-zero amplitude parameters and the set of location bits. The transceiver transmits the CSI to the base unit.

FIELD

The subject matter disclosed herein relates generally to wirelesscommunications and more particularly relates to preparing CSI.

BACKGROUND

The following abbreviations and acronyms are herewith defined, at leastsome of which are referred to within the following description.

Third Generation Partnership Project (“3GPP”), Access and MobilityManagement Function (“AMF”), Access Point Name (“APN”), Access Stratum(“AS”), Carrier Aggregation (“CA”), Clear Channel Assessment (“CCA”),Control Channel Element (“CCE”), Channel State Information (“CSI”),Common Search Space (“CSS”), Data Network Name (“DNN”), Data RadioBearer (“DRB”), Downlink Control Information (“DCI”), Downlink (“DL”),Enhanced Clear Channel Assessment (“eCCA”), Enhanced Mobile Broadband(“eMBB”), Evolved Node-B (“eNB”), Evolved Packet Core (“EPC”), EvolvedUMTS Terrestrial Radio Access Network (“E-UTRAN”), EuropeanTelecommunications Standards Institute (“ETSI”), Frame Based Equipment(“FBE”), Frequency Division Duplex (“FDD”), Frequency Division MultipleAccess (“FDMA”), Globally Unique Temporary UE Identity (“GUTI”), HybridAutomatic Repeat Request (“HARQ”), Home Subscriber Server (“HSS”),Internet-of-Things (“IoT”), Key Performance Indicators (“KPI”), LicensedAssisted Access (“LAA”), Load Based Equipment (“LBE”),Listen-Before-Talk (“LBT”), Long Term Evolution (“LTE”), LTE Advanced(“LTE-A”), Medium Access Control (“MAC”), Multiple Access (“MA”),Modulation Coding Scheme (“MC S”), Machine Type Communication (“MTC”),Massive MTC (“mMTC”), Mobility Management (“MM”), Mobility ManagementEntity (“MME”), Multiple Input Multiple Output (“MIMO”), Multipath TCP(“MPTCP”), Multi User Shared Access (“MUSA”), Non-Access Stratum(“NAS”), Narrowband (“NB”), Network Function (“NF”), Next Generation(e.g., 5G) Node-B (“gNB”), Next Generation Radio Access Network(“NG-RAN”), New Radio (“NR”), Policy Control & Charging (“PCC”), PolicyControl Function (“PCF”), Policy Control and Charging Rules Function(“PCRF”), Packet Data Network (“PDN”), Packet Data Unit (“PDU”), PDNGateway (“PGW”), Quality of Service (“QoS”), Quadrature Phase ShiftKeying (“QPSK”), Radio Access Network (“RAN”), Radio Access Technology(“RAT”), Radio Resource Control (“RRC”), Receive (“RX”),Switching/Splitting Function (“SSF”), Scheduling Request (“SR”), ServingGateway (“SGW”), Session Management Function (“SMF”), System InformationBlock (“SIB”), Transport Block (“TB”), Transport Block Size (“TBS”),Time-Division Duplex (“TDD”), Time Division Multiplex (“TDM”),Transmission and Reception Point (“TRP”), Transmit (“TX”), UplinkControl Information (“UCI”), Unified Data Management (“UDM”), UserEntity/Equipment (Mobile Terminal) (“UE”), Uplink (“UL”), User Plane(“UP”), Universal Mobile Telecommunications System (“UMTS”),Ultra-reliability and Low-latency Communications (“URLLC”), andWorldwide Interoperability for Microwave Access (“WiMAX”).

The wireless communication systems, CSI feedback is used to report oncurrent channel conditions. This is especially useful in FDD and FDMAsystems where the downlink (DL) and uplink (UL) channels are notreciprocal. With MU-MIMO and spatial multiplexing, a receiving device,such as a UE, may need to report channel conditions for multiplechannels or beams. Accordingly, much overhead is dedicated to CSIreporting in MU-MIMO and spatial multiplexing systems.

BRIEF SUMMARY

Methods for preparing channel state information (“CSI”) are disclosed.Apparatuses and systems also perform the functions of the methods. Onemethod (e.g., of a user equipment) includes communicating with a baseunit over a radio access network using spatial multiplexing. Here,multiple transmission layers are transmitted at a time, eachtransmission layer comprising multiple beams. The method includesidentifying a set of non-zero amplitude parameters over a set of layersand identifying a set of zero amplitude parameters over the set oflayers. The method includes computing a number of non-zero amplitudeparameters based on one or more of the set of non-zero amplitudeparameters and the set of zero amplitude parameters and determining anindication of the number of non-zero amplitude parameters. The methodincludes determining the location of zero amplitude parameters togenerate a set of location bits. The method includes preparing CSI,wherein the CSI includes the indication of the number of non-zeroamplitude parameters and the set of location bits and transmitting theCSI to the base unit.

In some embodiments, the determining the indication of the number ofnon-zero amplitude parameters includes computing a number of non-zeroamplitude parameters based on the set of non-zero amplitude parametersand encoding the number of non-zero amplitude parameters using avariable length code. In certain embodiments, determining the locationof zero amplitude parameters to generate the set of location bitsincludes generating the set of location bits using a combinatorialcoding or an enumerative coding. In some such embodiments, generatingthe set of location bits includes encoding the location of non-zeroamplitude parameters using the combinatorial coding or the enumerativecoding. In other such embodiments, generating the set of location bitsincludes encoding the location of zero amplitude parameters using thecombinatorial coding or the enumerative coding.

In some embodiments, the amplitude parameters are represented by bits,integers, or values in a range. In some embodiments, the amplitudeparameter is a beam amplitude.

In some embodiments, determining the indication of the number ofnon-zero amplitude parameters includes computing a number of zeroamplitude parameters based on the set of zero amplitude parameters andencoding the computed number of zero amplitude parameters. In suchembodiments, encoding the computed number of zero amplitude parametersincludes encoding using a variable length code. In some embodiments,preparing the CSI includes preparing a combined CSI for all of themultiple transmission layers.

BRIEF DESCRIPTION OF THE DRAWINGS

A more particular description of the embodiments briefly described abovewill be rendered by reference to specific embodiments that areillustrated in the appended drawings. Understanding that these drawingsdepict only some embodiments and are not therefore to be considered tobe limiting of scope, the embodiments will be described and explainedwith additional specificity and detail through the use of theaccompanying drawings, in which:

FIG. 1 is a schematic block diagram illustrating one embodiment of awireless communication system for efficiently preparing CSI using zeroamplitude parameters;

FIG. 2 is a block diagram illustrating one embodiment of a networkarchitecture for efficiently preparing CSI using zero amplitudeparameters;

FIG. 3 is a schematic block diagram illustrating one embodiment of auser equipment apparatus for preparing CSI using zero amplitudeparameters;

FIG. 4 is a schematic block diagram illustrating one embodiment of abase station apparatus for receiving CSI;

FIG. 5 is a block diagram illustrating one embodiment of antennaelements;

FIG. 6 is a block diagram illustrating one embodiment of a procedure forefficiently preparing CSI using zero amplitude parameters;

FIG. 7 is a diagram illustrating the number of bits needed to codewideband amplitudes according to a first embodiment of preparing CSI;

FIG. 8 is a diagram illustrating the number of bits needed to codewideband amplitudes according to a second embodiment of preparing CSI;

FIG. 9 is a flow chart diagram illustrating one embodiment of a methodfor efficiently preparing CSI; and

FIG. 10 is a flow chart flow chart diagram illustrating anotherembodiment of a method for efficiently preparing CSI using zeroamplitude parameters.

DETAILED DESCRIPTION

As will be appreciated by one skilled in the art, aspects of theembodiments may be embodied as a system, apparatus, method, or programproduct. Accordingly, embodiments may take the form of an entirelyhardware embodiment, an entirely software embodiment (includingfirmware, resident software, micro-code, etc.) or an embodimentcombining software and hardware aspects.

For example, the disclosed embodiments may be implemented as a hardwarecircuit comprising custom very-large-scale integration (“VLSI”) circuitsor gate arrays, off-the-shelf semiconductors such as logic chips,transistors, or other discrete components. The disclosed embodiments mayalso be implemented in programmable hardware devices such as fieldprogrammable gate arrays, programmable array logic, programmable logicdevices, or the like. As another example, the disclosed embodiments mayinclude one or more physical or logical blocks of executable code whichmay, for instance, be organized as an object, procedure, or function.

Furthermore, embodiments may take the form of a program product embodiedin one or more computer readable storage devices storing machinereadable code, computer readable code, and/or program code, referredhereafter as code. The storage devices may be tangible, non-transitory,and/or non-transmission. The storage devices may not embody signals. Ina certain embodiment, the storage devices only employ signals foraccessing code.

Any combination of one or more computer readable medium may be utilized.The computer readable medium may be a computer readable storage medium.The computer readable storage medium may be a storage device storing thecode. The storage device may be, for example, but not limited to, anelectronic, magnetic, optical, electromagnetic, infrared, holographic,micromechanical, or semiconductor system, apparatus, or device, or anysuitable combination of the foregoing.

More specific examples (a non-exhaustive list) of the storage devicewould include the following: an electrical connection having one or morewires, a portable computer diskette, a hard disk, a random-access memory(“RAM”), a read-only memory (“ROM”), an erasable programmable read-onlymemory (“EPROM” or Flash memory), a portable compact disc read-onlymemory (“CD-ROM”), an optical storage device, a magnetic storage device,or any suitable combination of the foregoing. In the context of thisdocument, a computer readable storage medium may be any tangible mediumthat can contain, or store a program for use by or in connection with aninstruction execution system, apparatus, or device.

Reference throughout this specification to “one embodiment,” “anembodiment,” or similar language means that a particular feature,structure, or characteristic described in connection with the embodimentis included in at least one embodiment. Thus, appearances of the phrases“in one embodiment,” “in an embodiment,” and similar language throughoutthis specification may, but do not necessarily, all refer to the sameembodiment, but mean “one or more but not all embodiments” unlessexpressly specified otherwise. The terms “including,” “comprising,”“having,” and variations thereof mean “including but not limited to,”unless expressly specified otherwise. An enumerated listing of itemsdoes not imply that any or all of the items are mutually exclusive,unless expressly specified otherwise. The terms “a,” “an,” and “the”also refer to “one or more” unless expressly specified otherwise.

As used herein, a list with a conjunction of “and/or” includes anysingle item in the list or a combination of items in the list. Forexample, a list of “A, B and/or C” includes only A, only B, only C, acombination of A and B, a combination of B and C, a combination of A andC or a combination of A, B and C. As used herein, a list using theterminology “one or more of” includes any single item in the list or acombination of items in the list. For example, one or more of A, B and Cincludes only A, only B, only C, a combination of A and B, a combinationof B and C, a combination of A and C or a combination of A, B and C. Asused herein, a list using the terminology “one of includes one and onlyone of any single item in the list. For example, “one of A, B and C”includes only A, only B or only C and excludes combinations of A, B andC. As used herein, “a member selected from the group consisting of A, B,and C,” includes one and only one of A, B, or C, and excludescombinations of A, B, and C.” As used herein, “a member selected fromthe group consisting of A, B, and C and combinations thereof” includesonly A, only B, only C, a combination of A and B, a combination of B andC, a combination of A and C or a combination of A, B and C.

Furthermore, the described features, structures, or characteristics ofthe embodiments may be combined in any suitable manner. In the followingdescription, numerous specific details are provided, such as examples ofprogramming, software modules, user selections, network transactions,database queries, database structures, hardware modules, hardwarecircuits, hardware chips, etc., to provide a thorough understanding ofembodiments. One skilled in the relevant art will recognize, however,that embodiments may be practiced without one or more of the specificdetails, or with other methods, components, materials, and so forth. Inother instances, well-known structures, materials, or operations are notshown or described in detail to avoid obscuring aspects of anembodiment.

Aspects of the embodiments are described below with reference toschematic flowchart diagrams and/or schematic block diagrams of methods,apparatuses, systems, and program products according to embodiments. Itwill be understood that each block of the schematic flowchart diagramsand/or schematic block diagrams, and combinations of blocks in theschematic flowchart diagrams and/or schematic block diagrams, can beimplemented by code. This code may be provided to a processor of ageneral-purpose computer, special purpose computer, or otherprogrammable data processing apparatus to produce a machine, such thatthe instructions, which execute via the processor of the computer orother programmable data processing apparatus, create means forimplementing the functions/acts specified in the schematic flowchartdiagrams and/or schematic block diagrams.

The code may also be stored in a storage device that can direct acomputer, other programmable data processing apparatus, or other devicesto function in a particular manner, such that the instructions stored inthe storage device produce an article of manufacture includinginstructions which implement the function/act specified in the schematicflowchart diagrams and/or schematic block diagrams.

The code may also be loaded onto a computer, other programmable dataprocessing apparatus, or other devices to cause a series of operationalsteps to be performed on the computer, other programmable apparatus, orother devices to produce a computer implemented process such that thecode which execute on the computer or other programmable apparatusprovide processes for implementing the functions/acts specified in theschematic flowchart diagrams and/or schematic block diagram.

The schematic flowchart diagrams and/or schematic block diagrams in theFigures illustrate the architecture, functionality, and operation ofpossible implementations of apparatuses, systems, methods, and programproducts according to various embodiments. In this regard, each block inthe schematic flowchart diagrams and/or schematic block diagrams mayrepresent a module, segment, or portion of code, which includes one ormore executable instructions of the code for implementing the specifiedlogical function(s).

It should also be noted that, in some alternative implementations, thefunctions noted in the block may occur out of the order noted in theFigures. For example, two blocks shown in succession may, in fact, beexecuted substantially concurrently, or the blocks may sometimes beexecuted in the reverse order, depending upon the functionalityinvolved. Other steps and methods may be conceived that are equivalentin function, logic, or effect to one or more blocks, or portionsthereof, of the illustrated Figures.

The description of elements in each figure may refer to elements ofproceeding figures. Like numbers refer to like elements in all figures,including alternate embodiments of like elements.

In spatial multiplexing, the inventors have observed that most of thetransmitted energy, e.g., 75% or more, is in the main beam of eachtransmission layer and that in about 85% of cases none of the selectedbeam vectors have zero amplitudes. The disclosed embodiments leveragethis information to improve coding efficiency of codebook parameters forCSI feedback using a Type II codebook. As understood in the art, Type IIcodebooks provide high resolution information about current channelconditions and are used in multi-user MIMO (“MU-MIMO”) scenarios, wherespatial multiplexing is used to increase the number of users and/or toincrease the transmission throughput (e.g., data bandwidth) for theusers. In various embodiments, a transmitter will transmit a beamformedCSI-specific reference signal (e.g., a “CSI-RS”) which the receiver usesto measure channel conditions. Generally, beamformed signals include amain beam and one or more remaining beams.

The present disclosure describes an improvement to coding a Type II CSIcodebook which facilitates instantaneous decoding of the main beamswithout affecting the coding efficiency. The improved codebook alsoincreases the efficiency for the case where none of the wideband beamamplitudes are zero, which is observed to be about 85% of the cases, atthe expense of losing some efficiency when some of the beams have zeroamplitudes. The improved codebook combines combinatorial coding with avariable length codeword that is based on the efficiency of thecombinatorial code.

FIG. 1 depicts a wireless communication system 100 for efficientlycoding CSI 150, according to embodiments of the disclosure. In oneembodiment, the wireless communication system 100 includes at least oneremote unit 105, an access network 120 containing at least one base unit110, wireless communication links 115, and a mobile core network 130.Even though a specific number of remote units 105, access networks 120,base units 110, wireless communication links 115, and mobile corenetworks 130 are depicted in FIG. 1, one of skill in the art willrecognize that any number of remote units 105, access networks 120, baseunits 110, wireless communication links 115, and mobile core networks130 may be included in the wireless communication system 100. In anotherembodiment, the access network 120 contains one or more WLAN (e.g.,Wi-Fi™) access points.

In one implementation, the wireless communication system 100 iscompliant with the 5G system specified in the 3GPP specifications (e.g.,“5G NR”). More generally, however, the wireless communication system 100may implement some other open or proprietary communication network, forexample, LTE or WiMAX, among other networks. The present disclosure isnot intended to be limited to the implementation of any particularwireless communication system architecture or protocol.

In one embodiment, the remote units 105 may include computing devices,such as desktop computers, laptop computers, personal digital assistants(“PDAs”), tablet computers, smart phones, smart televisions (e.g.,televisions connected to the Internet), smart appliances (e.g.,appliances connected to the Internet), set-top boxes, game consoles,security systems (including security cameras), vehicle on-boardcomputers, network devices (e.g., routers, switches, modems), or thelike. In some embodiments, the remote units 105 include wearabledevices, such as smart watches, fitness bands, optical head-mounteddisplays, or the like. Moreover, the remote units 105 may be referred toas subscriber units, mobiles, mobile stations, users, terminals, mobileterminals, fixed terminals, subscriber stations, UE, user terminals, adevice, or by other terminology used in the art. The remote units 105may communicate directly with one or more of the base units 110 viauplink (“UL”) and downlink (“DL”) communication signals. Furthermore,the UL and DL communication signals may be carried over the wirelesscommunication links 115.

The base units 110 may be distributed over a geographic region. Incertain embodiments, a base unit 110 may also be referred to as anaccess terminal, an access point, a base, a base station, a Node-B, aneNB, a gNB, a Home Node-B, a relay node, a device, aTransmission/Reception Point (“Tx/Rx Point” or “TRP”), or by any otherterminology used in the art. The base units 110 are generally part of aradio access network (“RAN”), such as the access network 120, that mayinclude one or more controllers communicably coupled to one or morecorresponding base units 110. These and other elements of the radioaccess network are not illustrated, but are well known generally bythose having ordinary skill in the art. The base units 110 connect tothe mobile core network 130 via the access network 120.

The base units 110 may serve a number of remote units 105 within aserving area, for example, a cell or a cell sector via a wirelesscommunication link 115. The base units 110 may communicate directly withone or more of the remote units 105 via communication signals.Generally, the base units 110 transmit downlink (“DL”) communicationsignals to serve the remote units 105 in the time, frequency, and/orspatial domain. Furthermore, the DL communication signals may be carriedover the wireless communication links 115. The wireless communicationlinks 115 may be any suitable carrier in licensed or unlicensed radiospectrum. The wireless communication links 115 facilitate communicationbetween one or more of the remote units 105 and/or one or more of thebase units 110.

In one embodiment, the mobile core network 130 is a 5G core (“5GC”) orthe evolved packet core (“EPC”), which may be coupled to other datanetwork 125, like the Internet and private data networks, among otherdata networks. Each mobile core network 130 belongs to a single publicland mobile network (“PLMN”). The present disclosure is not intended tobe limited to the implementation of any particular wirelesscommunication system architecture or protocol.

The mobile core network 130 includes several network functions (“NFs”).As depicted, the mobile core network 130 includes an access and mobilitymanagement function (“AMF”) 135, a session management function (“SMF”)140, and a user plane function (“UPF”) 145. Although a specific numberof AMFs 135, SMFs 140, and UPFs 145 are depicted in FIG. 1, one of skillin the art will recognize that any number and type of network functionmay be included in the mobile core network 130.

The AMF 135 provides services such as UE registration, UE connectionmanagement, and UE mobility management. The SMF 140 manages the datasessions of the remote units 105, such as a PDU session. The UPF 145provides user plane (e.g., data) services to the remote units 105. Adata connection between the remote unit 105 and a data network 125 ismanaged by a UPF 145.

To support spatial multiplexing and MU-MIMO, the remote unit 105provides CSI feedback 150 to the base unit 110, e.g., using a Type IIcodebook. As discussed above, the remote unit 105 may select a codewordfrom the CSI codebook, wherein the CSI codebook uses both combinatorialcoding and a variable length coding that is based on the efficiency ofthe combinatorial code. Here, the access network 120 and the remoteunits 105 all have copies of the same CSI codebook, wherein the remoteunit 105 provides CSI feedback 150 by transmitting a codeword from theCSI codebook.

As a first example, consider the coding of wideband parameters in caseof rank-2 (e.g., 2 transmission layers) codebook with the number ofantenna ports: 2 N₁×N₂=32, the number of beams: L=4 and each layer ofthe precoding matrix being linear combination of these L beams. Thequantities, N₁, N₂ denote the number of dual-polarized antenna elementsin two dimensions respectively. The factor of 2 accounts for the antennaarray being composed of two antenna elements, each sensitive toorthogonal polarization (e.g. horizontal and vertical). Here, the gainsof the linear combination coefficients used for combining the beams aredifferent for both the polarizations, thereby making total of eightpossible gains for each transmission layer (e.g., 4 beams×2polarizations). In this example, the subband parameters may still becoded using the old approach, for example, not coding those subbandparameters for which the wideband amplitude is zero.

In some embodiments, to prepare the CSI feedback, the remote unit 105may first identify and encode the main beam for each transmission layer.This is a departure from the conventional approach where the first stepis identifying all the L beams. Note that the main beam of each layercan be any of N₁×N₂=16 beams. When the two main beams are the same,there are a total of 16 possibilities (not including the polarizationpart). When the two mains beams are different, there are C(16,2)=120possibilities.

To code the main beams the remote unit 105 uses one bit to indicatewhether the main beam of both the transmission layers are the same ornot. For example, a value of ‘0’ may indicate the main beams being thesame, while a value of ‘1’ may indicate that they are different. Wherethe beams are the same, four bits are needed to identify the main beamfrom the 16 possibilities. Where the beams are different, seven bits areneeded to indicate the combination of main beams from the 120possibilities.

Additionally, the remote unit 105 uses one bit for each transmissionlayer to represent which polarization the main beam corresponds to.Accordingly, a total of nine bits are needed if the main beams aredifferent and a total of six bits are needed if they are same.

Next, the remote unit 105 identifies and codes the remaining beams. Forthe case where the main beams are the same, referred to herein as“Condition-A,” the remote unit identifies L−1 remaining beams. For thecase where the main beams are different, referred to herein as“Condition-B,” the remote unit 105 identifies L−2 remaining beams.

In case where two beams are the same, Condition-A, there are

${{C\left( {15,3} \right)} = {\begin{pmatrix}15 \\3\end{pmatrix} = {\frac{15 \times 14 \times 13}{6} = 455}}},$possible selections of remaining beams, thus needing 9 bits to representthe remaining L−1 beams. In case two main beams are different,Condition-B, there are

${{C\left( {14,2} \right)} = {\begin{pmatrix}14 \\2\end{pmatrix} = 91}},$possible selections for the remaining L−2 beams, which can berepresented in 7 bits. In both cases, combinatorial coding is used toindicate the remaining beams.

Using the most efficient coding in the prior are still requires11+3+3=17 bits to represent the set of L=4 beams and identify the mainbeams. In the improved coding described herein, coding all the beams andidentifying the main beams requires a maximum of 17 bits (e.g., 1+6+9=16for Condition-A, and 1+9+7=17 for Condition-B). Beneficially, theimproved coding approach facilitates instantaneous decoding of the mainbeams. Another advantage of this approach is that the base unit 110needs to decode at most 10 bits, instead of all 17 bits, to find themain beams.

In certain embodiments, such as about 15% of the cases, some of thewideband gains have a zero amplitude. Here, the remote unit 105 hasalready coded the main beams for the two transmission layers. At thispoint, there are seven more wideband beam amplitudes which need to becoded for each transmission layer. With two transmission layers, thereare a total of fourteen remaining amplitudes to code. Here, the remoteunit 105 uses a variable length code to code the number of non-zero beamamplitudes and uses enumerative or combinatorial coding to identify thebeams with zero amplitudes. In certain embodiments, the remote unit 105uses range coding to jointly combine the amplitudes of the non-zerobeams. As understood in the art, “range coding” is a data encodingtechnique similar to, yet different from, arithmetic coding. Thisresults in reduced codebook overhead for the large majority of caseswhere there are no non-zero beam vectors, even though codebook overheadincreases when there are some zero amplitude beam vectors.

Recall that in the case where the two main beams are the same(Condition-A), the remote unit 105 is able to code the widebandparameters using 16 bits instead of 17 bits, so there was direct savingof 1 bit in that situation. For Condition-A (e.g., where both the mainbeams are the same), the remote unit 105 indicates whether there are anyzero amplitude beam vectors by adding an extra bit to the coding ofremaining beams, thus using 10 bits instead of 9 bits to code theremaining L−1. For example, the added bit may be set to ‘0’ if none ofthe amplitudes of the remaining beam vectors in the two layers is zero;otherwise, the bit may be set to ‘1.’ The case where the two main beamsare different (Condition-B), the coding of the remaining beams is highlyinefficient (e.g., coding 91 values out of 128 possibilities with the 7bits). Here, the maximum codeword in this case, in binary, has a valueof ‘1011010.’ Because the coding does not have any mapped values thatbegin with ‘11,’ in some embodiments, the remote unit 105 uses avariable length codeword starting with ‘11 . . . ’ to indicate thatthere is a situation where at least one of the beam amplitudes is 0.

In some embodiments, the remote unit 105 prepares the CSI by identifyinga set of zero amplitude beams over a set of layers. The remote unit 105may compute and encode a number of zero amplitude beams based on the setof zero amplitude beams. Additionally, the remote unit may encode thelocation of zero amplitude beams to generate a set of zero-beamlocations bits. In such embodiments, the CSI comprises the code for thenumber of zero amplitude beams and the set of zero-beam location bits.The remote unit 105 transmits the CSI to the base unit 110. In someembodiments, the CSI may be communicated by selecting a CSI codewordfrom a CSI codebook.

In various embodiments, the remote unit 105 identifies a set of non-zeroamplitude parameters and a set of zero amplitude parameters over the setof layers. The remote unit 105 computes a number of non-zero amplitudeparameters and determines an indication of the number of non-zeroamplitude parameters. The remote unit 105 determines the location ofzero amplitude parameters to generate a set of location bits. The remoteunit 105 prepares CSI that includes the indication of the number ofnon-zero amplitude parameters and the set of location bits. The remoteunit 105 transmits the CSI to the base unit 110. In some embodiments,the CSI may be communicated by selecting a CSI codeword from a CSIcodebook.

FIG. 2 depicts a network architecture 200 used for efficiently preparingCSI using zero amplitude parameters, according to embodiments of thedisclosure. The network architecture 200 may be a simplified embodimentof the wireless communication system 100. As depicted, the networkarchitecture 200 includes a UE 205 in communication with a eNB 210. TheUE 205 may be one embodiment of a remote unit 105 and the eNB 210 may beone embodiment of the base unit 110, described above. Here, the eNB 210uses spatial multiplexing when communicating with the UE, where multipletransmission layers are transmitted, each layer having multiple beams.

As depicted, the eNB 210 transmits, on the downlink, various signalsincluding multiple reference signals (“RS”) (see signaling 220). Thesesignals pass through the communication channel 215, e.g., the physicaltransmission medium. As the signals pass through the communicationchannel 215, they gradually weaken and encounter objects which altertheir paths and degrade the signals. Upon receiving the downlinksignals, the UE 205 measures the channel conditions (e.g., the “channelstate”) based on the received reference signals (see block 225).

The UE 205 provides channel state information (“CSI”) feedback to theeNB 210, e.g., using a CSI codeword from a CSI codebook (see signaling230). Specifically, the UE 205 may select a codeword from the CSIcodebook based on the measured channel conditions and transmit thecodeword to the eNB 210. As the eNB 210 uses spatial multiplexing, theUE 205 selects (e.g., recommends) one codeword from a Type II Codebookto provide CSI feedback. In various embodiments, eNB 210 determines anoptimum precoding matrix for the current channel conditions based on theCSI feedback. Procedures for preparing the CSI are discussed below.

As used herein, a set of CSI codewords makes up the CSI codebook. Theset of codewords in the CSI codebook may be parameterized by a set ofparameters such that every combination of the parameters corresponds tocodewords, and the set of codewords that are generated by allcombinations of the parameters is the codebook. These parameters may berepresented using bits, integers, or other values in a range (e.g., from1 to some number). Here, the CSI codebook is coded using the improvedapproaches described herein, with beam information being the parametersused to select the codeword. When preparing the codeword, the UE 205encodes the beam information using the described approaches to derivethe codeword.

FIG. 3 depicts one embodiment of a user equipment apparatus 300 that maybe used for preparing CSI using zero amplitude parameters, according toembodiments of the disclosure. The user equipment apparatus 300 may beone embodiment of the remote unit 105 and/or UE 205. Furthermore, theuser equipment apparatus 300 may include a processor 305, a memory 310,an input device 315, a display 320, and a transceiver 325. In someembodiments, the input device 315 and the display 320 are combined intoa single device, such as a touch screen. In certain embodiments, theuser equipment apparatus 300 may not include any input device 315 and/ordisplay 320.

As depicted, the transceiver 325 includes at least one transmitter 330and at least one receiver 335. Additionally, the transceiver 325 maysupport at least one network interface 340. Here, the at least onenetwork interface 340 facilitates communication with an eNB or gNB(e.g., using the Uu interface). Additionally, the at least one networkinterface 340 may include an interface used for communications with anetwork function in the mobile core network 130, such as an N1 interfaceused to communicate with the AMF 135. The transceiver 325 is configuredto communicate with a transmit-receive point (“TRP”), such as the baseunit 110 and/or the eNB 210, in a radio access network using spatialmultiplexing, wherein multiple transmission layers are transmitted at atime, each transmission layer comprising multiple beams.

The processor 305, in one embodiment, may include any known controllercapable of executing computer-readable instructions and/or capable ofperforming logical operations. For example, the processor 305 may be amicrocontroller, a microprocessor, a central processing unit (“CPU”), agraphics processing unit (“GPU”), an auxiliary processing unit, a fieldprogrammable gate array (“FPGA”), or similar programmable controller. Insome embodiments, the processor 305 executes instructions stored in thememory 310 to perform the methods and routines described herein. Theprocessor 305 is communicatively coupled to the memory 310, the inputdevice 315, the display 320, and the transceiver 325.

In some embodiments, the processor 305 identifies a main beam for eachof the multiple transmission layers. During spatial multiplexing, thetransceiver 325 may receive multiple beams and multiple transmissionlayers. The main beam (also referred to as a first beam) contains themajority of the transmission energy, for example greater than 70% of thetransmitted power. The remainder of the energy is in the remaining beams(also referred to as secondary beams). Having identified the main beamsfor each transmission layer, the processor 305 determines whether themain beams are the same (e.g., are associated with the same antennaelement) for each of the multiple transmission layers. Alternatively,the processor 305 determines whether the main beams are the same for thefirst two transmission layers or for each pair of transmission layers.

Additionally, the processor 305 prepares a channel state information(“CSI”) codeword and controls the transceiver 425 to send the CSIcodeword to the TRP. Here, the CSI codeword includes a first bit thatindicating whether the main beams of each transmission layer are thesame. The CSI codeword also includes a first set of bits coding the mainbeams and a second set of bits coding the remaining beams. In variousembodiments, the CSI codeword belongs to a Type II codebook for CSIfeedback.

In certain embodiments, the first set of bits coding the main beamsincludes one bit to indicate a main beam polarization for eachtransmission layer. In certain embodiments, the second set of bitscoding the remaining beams uses combinatorial coding to indicate theremaining beams.

In certain embodiments, the number of transmission layers is two and themain beams are the same (e.g., Condition-A). Here, preparing the CSIcodeword includes using enumerative coding to indicate a beam index ofthe main beam, in the first set of bits coding the main beam. In suchembodiments, the CSI codeword may further include one bit to indicatewhether the remaining beams all have non-zero wideband amplitudes. Whereat least one remaining beam has a wideband amplitude of zero, then thesecond set of bits coding the remaining beams includes a variable lengthcodeword to identify the at least one remaining beam having a widebandamplitude of zero.

In certain embodiments, the number of transmission layers is two and themain beams are not the same (e.g., Condition-B). Here, preparing the CSIcodeword includes using combinatorial coding to indicate a combinationof beam indexes corresponding to the main beams of the two transmissionlayers, in the first set of bits coding the main beams. In suchembodiments, the second set of bits coding the remaining beams includesa variable length codeword with a specific prefix to indicate whether atleast one of the remaining beams have a wideband amplitude of zero.Moreover, the remaining bits of the variable length code word are usedto identify the at least one remaining beam having a wideband amplitudeof zero. The length of the specific prefix, L_(p), is derived from theefficiency of the combinatorial code, E, using a ceiling function and isgiven by the following equation:L _(p)=┌−log₂(1−2^(E-1))┐,  Equation 1

Here, the coding efficiency, E, is defined using the following equation,where X represents the number of values representable by the number ofbits and Y represents the number of combinations that are coded:E=1−(log₂ X−log₂ Y),  Equation 2

Note that for Condition-A, we have added an extra bit and hence we cansay that efficiency is close to zero so the specific prefix forCondition-A has length of one, as calculated using Equation 1.Similarly, for Condition-B, efficiency calculated using Equation 2 is0.51 and hence the length of the specific prefix calculated usingEquation 1 is 2. The specific prefix is designed as all ones of lengthLp.

In one embodiment, the second set of bits coding the remaining beamsuses range coding to combine the amplitude of each remaining beam havinga non-zero wideband amplitude with another CSI parameter.

In various embodiments, the processor 305 identifies a set of zeroamplitude beams over a set of layers. Additionally, the processor 305computes the number of zero amplitude beams based on the set of zerobeams and encodes the number of zero amplitude beams.

In various embodiments, the processor 305 encodes the location of zeroamplitude beams to generate a set of zero-beam locations bits. In someembodiments, the processor 305 encodes the location of zero amplitudebeams to generate the set of zero location bits using a combinatorialcoding. In some embodiments, the processor 305 encodes the location ofzero amplitude beams to generate the set of zero location bits using anenumerative coding.

The processor 305 prepares a channel state information (“CSI”) codebook,wherein the CSI codebook comprises the encoded number of zero amplitudebeams and the set of zero-beam location bits, wherein the transceiver325 transmits the CSI codebook to the TRP. In some embodiments, theprocessor 305 prepares a CSI codebook by preparing a combined CSIcodebook for all of the multiple transmission layers.

In some embodiments, the multiple transmission layers are furtherdivided into a set of pairs of layers. In such embodiments, theprocessor 305 may prepare a CSI codebook for each pair in the set ofpairs of layers, wherein each CSI codebook comprises the encoded numberof zero amplitude beams and the set of zero-beam location bits. In someembodiments, the CSI codebook includes an additional bit to indicate ifthere is a zero beam in the set of layers.

In certain embodiments, the processor 305 encodes the number of zeroamplitude beams using a variable length code. In one embodiment, theprocessor 305 encodes the location of zero amplitude beams to generatethe set of zero location bits using a combinatorial coding. In anotherembodiment, the processor 305 encodes the location of zero amplitudebeams to generate the set of zero location bits using an enumerativecoding. In certain embodiments, the processor 305 identifies a number ofnon-zero amplitude beams over the multiple transmission layers andencodes the identified number of non-zero amplitude beams.

In various embodiments, the processor 305 identifies a set of non-zeroamplitude parameters over a set of layers and identifies a set of zeroamplitude parameters over the set of layers. Moreover, the processor 305may compute the number of non-zero amplitude parameters based on eitherthe set of non-zero amplitude parameters or the set of zero amplitudeparameters (or using both set).

The processor 305 determines an indication of the number of non-zeroamplitude parameters. Note that the parameters may have either zeroamplitude or a non-zero amplitude. As such, there is a reciprocalrelationship between the number of zero amplitude parameters and thenumber of non-zero amplitude parameters, so that the number of zeroamplitude parameters can be inferred from knowledge of the number ofnon-zero amplitude parameters, and vice versa.

Additionally, the processor 305 may determine the location of zeroamplitude parameters to generate a set of location bits. Here, there isa finite number of locations (e.g., beam locations) among the set oflayers. Due to the reciprocal relationship between the number of zeroamplitude parameters and the number of non-zero amplitude parameters,there is a reciprocal relationship between the location of zeroamplitude parameters and the location of non-zero amplitude parameters,so that the location of zero amplitude parameters can be inferred fromknowledge of the location of non-zero amplitude parameters, and viceversa.

Having generated the set of location bits, the processor 305 preparesCSI. Here, the CSI includes the indication of the number of non-zeroamplitude parameters and the set of location bits. The processor 305controls the transceiver 325 to transmit the CSI to the base unit.

In some embodiments, the processor 305 determines the indication of thenumber of non-zero amplitude parameters by encoding the number ofnon-zero amplitude parameters, for example using a variable length code.Here, the indication of the number of non-zero amplitude parametersincluded in the CSI is the representation of number of non-zeroamplitude parameters generated using the variable length code. Incertain embodiments, the amplitude parameters are represented by bits,integers, or values in a range. In certain embodiments, the amplitudeparameter is a beam amplitude. In various embodiments, the amplitudeparameters may be referred to as “coefficients.”

In some embodiments, the processor 305 generates the set of locationbits by encoding the location of zero amplitude parameters using acombinatorial coding. Alternatively, the processor 305 may encode thelocation of zero amplitude parameters using an enumerative coding. Inother embodiments, the processor 305 may generates the set of locationbits by encoding the location of non-zero amplitude parameters using acombinatorial coding. Alternatively, the processor 305 may encode thelocation of non-zero amplitude parameters using an enumerative coding.

In some embodiments, the processor 305 determines the indication of thenumber of non-zero amplitude parameters by encoding the number of zeroamplitude parameters. In certain embodiments, the number of zeroamplitude parameters is encoded using a variable length code. Recallthat knowledge of the number of non-zero amplitude parameters can beinferred from knowledge of the number of zero amplitude parameters.Here, the indication of the number of non-zero amplitude parametersincluded in the CSI is the representation of number of zero amplitudeparameters generated, e.g., using the variable length code.

In some embodiments, the processor 305 prepares the CSI by preparing acombined CSI for all of the multiple transmission layers. In otherembodiments, the processor 305 may prepare the CSI by preparing a CSIfor each pair of layers from the set of all of the multiple transmissionlayers. As noted above, determining the location of zero amplitudeparameters to generate the set of location bits may include theprocessor 305 generating the set of location bits using a combinatorialcoding or an enumerative coding.

The memory 310, in one embodiment, is a computer readable storagemedium. In some embodiments, the memory 310 includes volatile computerstorage media. For example, the memory 310 may include a RAM, includingdynamic RAM (“DRAM”), synchronous dynamic RAM (“SDRAM”), and/or staticRAM (“SRAM”). In some embodiments, the memory 310 includes non-volatilecomputer storage media. For example, the memory 310 may include a harddisk drive, a flash memory, or any other suitable non-volatile computerstorage device. In some embodiments, the memory 310 includes bothvolatile and non-volatile computer storage media. In some embodiments,the memory 310 stores data relating to preparing CSI, for example beamindices, beam amplitudes, codebooks, precoding matrices, and the like.In certain embodiments, the memory 310 also stores program code andrelated data, such as an operating system or other controller algorithmsoperating on the user equipment apparatus 300 and one or more softwareapplications.

The input device 315, in one embodiment, may include any known computerinput device including a touch panel, a button, a keyboard, a stylus, amicrophone, or the like. In some embodiments, the input device 315 maybe integrated with the display 320, for example, as a touchscreen orsimilar touch-sensitive display. In some embodiments, the input device315 includes a touchscreen such that text may be input using a virtualkeyboard displayed on the touchscreen and/or by handwriting on thetouchscreen. In some embodiments, the input device 315 includes two ormore different devices, such as a keyboard and a touch panel.

The display 320, in one embodiment, may include any known electronicallycontrollable display or display device. The display 320 may be designedto output visual, audible, and/or haptic signals. In some embodiments,the display 320 includes an electronic display capable of outputtingvisual data to a user. For example, the display 320 may include, but isnot limited to, an LCD display, an LED display, an OLED display, aprojector, or similar display device capable of outputting images, text,or the like to a user. As another, non-limiting, example, the display320 may include a wearable display such as a smart watch, smart glasses,a heads-up display, or the like. Further, the display 320 may be acomponent of a smart phone, a personal digital assistant, a television,a table computer, a notebook (laptop) computer, a personal computer, avehicle dashboard, or the like.

In certain embodiments, the display 320 includes one or more speakersfor producing sound. For example, the display 320 may produce an audiblealert or notification (e.g., a beep or chime). In some embodiments, thedisplay 320 includes one or more haptic devices for producingvibrations, motion, or other haptic feedback. In some embodiments, allor portions of the display 320 may be integrated with the input device315. For example, the input device 315 and display 320 may form atouchscreen or similar touch-sensitive display. In other embodiments,the display 320 may be located near the input device 315.

The transceiver 325 communicates with one or more network functions of amobile communication network. The transceiver 325 operates under thecontrol of the processor 305 to transmit messages, data, and othersignals and also to receive messages, data, and other signals. Forexample, the processor 305 may selectively activate the transceiver (orportions thereof) at particular times in order to send and receivemessages. The transceiver 325 may include one or more transmitters 330and one or more receivers 335. To support spatial multiplexing and/orbeamforming, the transceiver 325 may include multiple transmitters 330and/or multiple receivers 335.

FIG. 4 depicts one embodiment of a base station apparatus 400 that maybe used for receiving CSI, according to embodiments of the disclosure.The base station apparatus 400 may be one embodiment of the base unit110 and/or the eNB 210. Furthermore, the base station apparatus 400 mayinclude a processor 405, a memory 410, an input device 415, a display420, and a transceiver 425. In some embodiments, the input device 415and the display 420 are combined into a single device, such as a touchscreen. In certain embodiments, the base station apparatus 400 may notinclude any input device 415 and/or display 420.

As depicted, the transceiver 425 includes at least one transmitter 430and at least one receiver 435. Additionally, the transceiver 425 maysupport at least one network interface 440. Here, the at least onenetwork interface 440 facilitates communication with a remote unit (suchas the remote unit 105 and/or UE 205). Additionally, the at least onenetwork interface 440 may include an interface used for communicationswith one or more network functions in a mobile network core, such as theN1 interface for communicating with the AMF 135.

In various embodiments, the transceiver 425 communicates with one ormore remote units using spatial multiplexing, wherein multipletransmission layers are transmitted at a time, each transmission layercomprising multiple beams. To support spatial multiplexing, thetransceiver 425 will include multiple transmitters 430 and receivers435. As discussed above, the transceiver 425 transmits various downlinksignals, including reference signals. The remote units determine thestate of the physical channel (e.g., of the communication medium) basedon the reference signals and send CSI feedback to the base stationapparatus 400. Accordingly, the transceiver may receive a CSI codewordfrom a remote unit, the CSI codeword selected from a CSI codebook usingparameters as described herein.

The processor 405, in one embodiment, may include any known controllercapable of executing computer-readable instructions and/or capable ofperforming logical operations. For example, the processor 405 may be amicrocontroller, a microprocessor, a central processing unit (“CPU”), agraphics processing unit (“GPU”), an auxiliary processing unit, a fieldprogrammable gate array (“FPGA”), or similar programmable controller. Insome embodiments, the processor 405 executes instructions stored in thememory 410 to perform the methods and routines described herein. Theprocessor 405 is communicatively coupled to the memory 410, the inputdevice 415, the display 420, and the transceiver 425.

In some embodiments, the processor 405 is configured to decode a Type IICSI codeword that is encoded according to the embodiments describedherein. Here, the processor 405 examines the first bit of the codewordto identify whether the main beams are the same for each transmissionlayer (or each pair of transmission layers). Then the processor 405identifies a first set of bits that encode the main beam. Note that thelength of the first set of bits varies based on whether the main beamsare the same. For Condition-A, the length of the first set of bitsdepends on the number of antenna elements (N₁×N₂), which is known to thebase station apparatus 400. For Condition-B, the length of the first setof bits depends on the number of antenna elements (N₁×N₂) and the numberof transmission layers being coded, which is known to the base stationapparatus 400.

The processor 405 further identifies a second set of bits that encodethe remaining beams. Again, that the length of the second set of bitsvaries based on whether the main beams are the same. As there is atleast one more remaining beam in Condition-A than in Condition-B, thelength of the second set of bits is longer for Condition-A than forCondition-B.

In certain embodiments, enumerative coding is used to identify the mainbeam in Condition-A and combinatorial coding is used to identify themain beams in Condition-B. Moreover, combinatorial coding may be used toindicate the remaining beams. Where at least one remaining beam has awideband amplitude of zero, then the second set of bits may include avariable length codeword having a specific prefix to indicate thissituation, with the remaining bits of the variable length codeword beingused to identifying the remaining beam(s) having a wideband amplitude ofzero. Here, the length of the specific prefix is based on the codingefficiency of the combinatorial code used to indicate the remainingbeams. In one embodiment, the specific prefix is all values of ‘1’ inthe length determined by the coding efficiency.

Moreover, the second set of bits coding the remaining beams may userange coding to jointly combine the amplitudes of each remaining beamhaving a non-zero wideband amplitude. Where the coding efficiency of thecombinatorial code used to indicate the remaining beams is sufficientlyinefficient, then the second set of bits coding the remaining beams mayuse range coding to combine the amplitude of each remaining beam havinga non-zero wideband amplitude with another CSI parameter, thus savingbits and improving the overall coding efficiency of the CSI codebook.Here, the parameter combined with the second set of bits is known to thebase station apparatus 400.

In some embodiments, the processor 405 may prepare a UL CSI codewordusing parameters and procedures described herein. For example, theprocessor 405 may generate a UL CSI codeword having a first bitindicating whether the main beams of each transmission layer are thesame, a first set of bits coding the main beams, and a second set ofbits coding the remaining beams. The processor 405 may further controlthe transceiver 425 to send the UL CSI codeword, e.g., to a remote unit.As another example, the processor 405 may prepare UL CSI by indicating anumber of non-zero amplitude parameters (e.g., non-zero coefficients)and a set of location bits, e.g., indicating locations of zero amplitudeparameters (e.g., zero coefficients). As discussed above, the indicationof the number of non-zero coefficients may be an encoding of the numberof zero coefficients or the number of non-zero coefficients.Additionally, the location bits may be an encoding of the location ofzero coefficients or the location of non-zero coefficients.

The memory 410, in one embodiment, is a computer readable storagemedium. In some embodiments, the memory 410 includes volatile computerstorage media. For example, the memory 410 may include a RAM, includingdynamic RAM (“DRAM”), synchronous dynamic RAM (“SDRAM”), and/or staticRAM (“SRAM”). In some embodiments, the memory 410 includes non-volatilecomputer storage media. For example, the memory 410 may include a harddisk drive, a flash memory, or any other suitable non-volatile computerstorage device. In some embodiments, the memory 410 includes bothvolatile and non-volatile computer storage media. In some embodiments,the memory 410 stores data relating to receiving CSI, for example beamindices, beam amplitudes, codebooks, precoding matrices, and the like.In certain embodiments, the memory 410 also stores program code andrelated data, such as an operating system or other controller algorithmsoperating on the base station apparatus 400 and one or more softwareapplications.

The input device 415, in one embodiment, may include any known computerinput device including a touch panel, a button, a keyboard, a stylus, amicrophone, or the like. In some embodiments, the input device 415 maybe integrated with the display 420, for example, as a touchscreen orsimilar touch-sensitive display. In some embodiments, the input device415 includes a touchscreen such that text may be input using a virtualkeyboard displayed on the touchscreen and/or by handwriting on thetouchscreen. In some embodiments, the input device 415 includes two ormore different devices, such as a keyboard and a touch panel.

The display 420, in one embodiment, may include any known electronicallycontrollable display or display device. The display 420 may be designedto output visual, audible, and/or haptic signals. In some embodiments,the display 420 includes an electronic display capable of outputtingvisual data to a user. For example, the display 420 may include, but isnot limited to, an LCD display, an LED display, an OLED display, aprojector, or similar display device capable of outputting images, text,or the like to a user. As another, non-limiting, example, the display420 may include a wearable display such as a smart watch, smart glasses,a heads-up display, or the like. Further, the display 420 may be acomponent of a smart phone, a personal digital assistant, a television,a table computer, a notebook (laptop) computer, a personal computer, avehicle dashboard, or the like.

In certain embodiments, the display 420 includes one or more speakersfor producing sound. For example, the display 420 may produce an audiblealert or notification (e.g., a beep or chime). In some embodiments, thedisplay 420 includes one or more haptic devices for producingvibrations, motion, or other haptic feedback. In some embodiments, allor portions of the display 420 may be integrated with the input device415. For example, the input device 415 and display 420 may form atouchscreen or similar touch-sensitive display. In other embodiments,the display 420 may be located near the input device 415.

The transceiver 425 communicates with one or more network functions of amobile communication network. The transceiver 425 operates under thecontrol of the processor 405 to transmit messages, data, and othersignals and also to receive messages, data, and other signals. Forexample, the processor 405 may selectively activate the transceiver (orportions thereof) at particular times in order to send and receivemessages. To support spatial multiplexing and beamforming, thetransceiver 425 may include multiple transmitters 430 and/or multiplereceivers 435.

FIG. 5 depicts an array 500 of antenna elements 505, according tovarious embodiments of the disclosure. Here, the antenna elements 505are arranged into a 4×4 grid. As depicted, each antenna elements 505 hasan index and the location of each antenna elements 505 may be describedusing coordinates of a first dimension 510 and a second dimension 515.For example, the antenna elements 505 of index 7 may be described usingthe coordinates {3,1} and the antenna elements 505 of index 12 may bedescribed using the coordinates {3,0}. Note that the beam index may beidentified using a 4-bit value. In some embodiments, each antennaelements 505 is a dual-polarized antenna element comprising two physicalelements, each sensitive to orthogonal polarization.

An antenna port may correspond to one or more physical network elements.In certain embodiments, an antenna port corresponds to a set oforthogonally arranged antenna elements, such that the antenna port mayproduce a beam with a first polarization or a second polarizationorthogonal to the first polarization. Thus, a dual-polarized antennaelement may correspond to two antenna ports, one for each orthogonalpolarization. In various embodiments, preparing a CSI codeword includesidentifying a beam index of the main beam of a transmission layer. Here,the beam index may be the index of the corresponding (dual-polarized)antenna element. In certain embodiments, the CSI codeword usescombinatorial coding to identify the beam indexes of the main beams ofmultiple transmission layers.

FIG. 6 depicts a procedure 600 for efficiently preparing CSI using zeroamplitude parameters, according to various embodiments of thedisclosure. The procedure 600 may be performed by a communication devicepreparing a codeword from a CSI type II codebook, such as the remoteunit 105, the UE 205, and/or the user equipment apparatus 300, describedabove. The procedure 600 assumes that N₁×N₂ is 16 (e.g., there are 16antenna elements resulting in 32 antenna ports) and that there are twotransmission layers. The number of beams is represented by L.

At block 605, the communication device identifies the main beams of bothtransmission layers (instead of identifying the L beams in theconventional approach). The main beam for each transmission layer may bethe same or different. Moreover, the main beam of each transmissionlayer can be any of N₁×N₂=16 beams (ignoring the polarization part).

At decision block 610, the communication device determines whether themain beams are the same. In response to the main beams being the same,the communication device determines the Condition-A applies (see block615) and codes the main beam (see block 620). Because in Condition-Athere are sixteen possibilities for the main beam, only four bits areneeded to code the main beam. Note that one bit for each layer is neededto represent which polarization the main beam corresponds to, thus atotal of six bits are required to code the main beams in Condition-A. Atblock 625, the communication device codes the remaining beams (L−1beams) using combinatorial coding. The number of bits needed for thecombinatorial coding of the remaining beams in Condition-A, N_(A), isdetermined using the following equation:

$\begin{matrix}\begin{matrix}{N_{A} = {\log_{2}\left( {C\left( {\left( {\left( {N_{1} \times N_{2}} \right) - 1} \right),\left( {L - 1} \right)} \right)} \right)}} \\{{= {\log_{2}\begin{pmatrix}\left( {\left( {N_{1} \times N_{2}} \right) - 1} \right) \\\left( {L - 1} \right)\end{pmatrix}}},}\end{matrix} & {{Equation}\mspace{14mu} 3}\end{matrix}$

Where L equals four, the number of bits, N_(A), is 9 due to there being455 possible selections (e.g., C(15,3)=455).

In contrast, in response to the main beams not being the same, thecommunication device determines the Condition-B applies (see block 630)and codes the main beam using combinatorial coding (see block 635). InCondition-B there are 120 possibilities (e.g., due to C(16,2)=120). Thisrequires seven bits to code the two main beams. Again, one bit for eachlayer is needed to represent which polarization the main beamcorresponds to, thus a total of nine bits are required to code the mainbeams in Condition-B. At block 640, the communication device codes theremaining beams (L−2 beams) using combinatorial coding. The number ofbits needed for the combinatorial coding of the remaining beams inCondition-B, N_(B), is determined using the following equation:

$\begin{matrix}\begin{matrix}{N_{B} = {\log_{2}\left( {C\left( {\left( {\left( {N_{1} \times N_{2}} \right) - 2} \right),\left( {L - 2} \right)} \right)} \right)}} \\{{= {\log_{2}\begin{pmatrix}\left( {\left( {N_{1} \times N_{2}} \right) - 2} \right) \\\left( {L - 2} \right)\end{pmatrix}}},}\end{matrix} & {{Equation}\mspace{14mu} 4}\end{matrix}$

Where L equals four, the number of bits, N_(B), is 7 due to there being91 possible selections (e.g., C(14,2)=91). After both coding the mainbeam(s) and coding the remaining beams, the communication device findsthe efficiency of the combinatorial code (see block 645), for exampleusing Equation 2.

In Condition-A, 455 combinations are coded out of a possible 512 valuesrepresentable by 9 bits, thus the combinatorial coding of the remainingbeams has an efficiency of E=0.83. In Condition-B, 91 combinations arecoded out of a possible 128 values representable by 7 bits, thus thecombinatorial coding of the remaining beams has an efficiency of E=0.51.Clearly, the combinatorial coding of the remaining beams in Condition-Bis fairly inefficient.

At block 650, the communication device designs a variable-length codefor the number of non-zero gains based on the calculated efficiency. Thevariable-length codeword is further discussed below with reference toFIGS. 7 and 8. Here, under Condition-B, the codeword for L−2 beams canbe combined with other parameters (e.g., using range coding) to improvethe overall coding efficiency. FIG. 8 depicts one example of combiningparameters in order to improve coding efficiency.

Using conventional coding, 17 bits (11+3+3) are needed to represent aset of L=4 beams and to identify the main beams. In Condition-A, only 16bits are needed (e.g., 1 indicating that the layers have the same mainbeam, 6 for coding the main beam, and 9 for coding the remaining beams),resulting in a bit savings of 1 as compared to previous Type II Codebookcoding. In Condition-B, 17 bits are needed (e.g., 1 indicating that thelayers have different main beams, 9 for coding the main beamcombination, and 7 for coding the remaining beams). Beneficially, theprocedure 600 facilitates instantaneous decoding of the main beams.Moreover, the TRP only needs to decode a most 10 bits (instead of theconventional 17 bits) in order to find the main beams using thedisclosed codebook.

FIG. 7 depicts a first table 700 illustrating the number of bits neededto code wideband amplitudes for the remaining beams, according tovarious embodiments of the disclosure. Here, it is assumed that N₁×N₂ is16 (e.g., there are 16 antenna elements and 32 antenna ports), thatthere are two transmission layers and two polarizations, and that thenumber of beams, L, is 4. With two polarizations and four beams, eachlayer has a total of eight possible wideband gains (amplitudes), for atotal of 16 amplitudes to code. The table 700 includes a column with thenumber of zeros, N_(Z), and a column with the number of bits torepresent the zero locations, a. The value of a is calculated using thefollowing equation:a=log₂(C(14,N _(Z)))  Equation 5

Here, C(14, N_(Z)) is the combination of 14 and N_(Z). The values of 14is selected as this is the number of remaining amplitudes (e.g., the 16amplitudes less the two main beams). Note that with four beams (e.g.,(N₁×N₂)−2). In other embodiments, the value of 14 in Equation 5 may bereplaced with NR, where NR represents the number of number of remainingamplitudes (e.g., after coding the main beams of each transmissionlayer). Note that the values of a are not integer values. This is due tothe inefficiency of the combinatorial code used to represent the zerolocations.

The table 700 also includes a column with the number of bits needed tocode the wideband amplitudes, b. The value of b can be calculated usingthe following equation:b=(14−N _(Z))×log₂(7)  Equation 6

Again, 14 is the number of remaining amplitudes and, in otherembodiments, the value of 14 may be replaced with NR in Equation 6. Asdiscussed above, inefficient combinatorial codes may be combined withother parameters, in order to improve efficiency and save bits. Incertain embodiments, different coding techniques may be used whencombining parameters to improve the coding efficiency. An example ofcombining parameters to improve efficiency is show in FIG. 8.

The table 700 includes a column with the total number of bits, c, neededto indicate the zero locations and the remailing wideband amplitudes.The table 700 also shows a variable length codeword used to signalN_(Z). Also included is a column with a sum of the total number of bits,c, and the length of the variable length codeword. Additionally, thetable 700 includes a column with the bit savings for each value ofN_(Z). Recall, that the most efficient prior art coding requires 42 bitsto code the wideband amplitudes of the secondary beams.

As shown, there is bit savings when there are no zero amplitude beams,which is the case about 85% of the time. However, there is an increasein the number of bits needed to code wideband amplitudes when number ofzero (N_(Z)) wideband amplitudes are 1, 2, 3 and 4. Recall that if anywideband amplitude is zero, then the corresponding sideband phase andsideband amplitude is not coded. Thus, even after using few extra bitsfor coding of wideband amplitudes, the coding described herein will notincrease the worst-case bits and in fact there is a saving on theworst-case bits for the improved coding of Type II codebook as describedherein.

Note that under Condition-B, the number of bits needed the are one morethan the number of bits needed to code under Condition-A. Also note,that for Condition-B, the first two bits of the variable length codewordare used to identify whether there are some zero wideband amplitudes.Even so, Condition-B needs 7 bits to code the L−2 remaining beams whileusing only 91 combinations out of possible 128. This makes the codewordhighly inefficient, as discussed above. When parameters areinefficiently coded, parameters may be combined, e.g., with rangecoding, to improve efficiency.

FIG. 8 depicts a second table 800 illustrating the number of bits neededto code beam location and wideband amplitudes for remaining beams,according to various embodiments of the disclosure. Here, it is assumedthe N₁×N₂ is 16 (e.g., there are 16 antenna elements resulting in 32antenna ports) and there are two transmission layers. In the table 800,the locations of the remaining beams are combined with the amplitudeinformation to improve coding efficiency, thereby saving an additionalbit in the Condition-B. Thus, by including the beam locationinformation, the codeword length for Condition-A and Condition-B becomethe same. In various embodiments, the remaining beam information (e.g.,both location and amplitude information) uses range encoding.

As depicted, the table 800 includes a column with the number of zeros,N_(Z), a column with the number of bits to represent the zero locations,a (calculated using the Equation 4), and a column with the number ofbits needed to code the wideband amplitudes, b (calculated using theEquation 5). The table 800 also includes a column with the number ofbits needed to indicate the location of the L-2 beams (here, the fixedvalue of 6.51) and total number of bits, d, needed to indicate the zerolocations, the remailing wideband amplitudes, and the beam locations.The table 800 also shows a variable length codeword used to signalN_(Z). Also included is a column with a sum of the total number of bits,c, and the length of the variable length codeword. Additionally, thetable 800 includes a column with the bit savings for each value ofN_(Z). Note, that the most efficient prior art coding requires 49 bits(e.g., 42+7) to code the wideband amplitudes and beam locations of thesecondary beams.

As shown, there is improved bit savings when there are no zero amplitudebeams, which is the case about 85% of the time. Moreover, the combinedparameter coding approach requires fewer additional bits, as compared tothe table 700, for the situations where there are 1, 2, 3, or 4.

FIG. 9 depicts a method 900 for efficiently preparing CSI using zeroamplitude parameters, according to embodiments of the disclosure. Insome embodiments, the method 900 is performed by an apparatus, such asthe remote unit 105, the UE 205, and/or the user equipment apparatus300. In certain embodiments, the method 900 may be performed by aprocessor executing program code, for example, a microcontroller, amicroprocessor, a CPU, a GPU, an auxiliary processing unit, a FPGA, orthe like.

The method 900 begins with communicating 905 with a transmit-receivepoint (“TRP”) over a radio access network using spatial multiplexing.Here, multiple transmission layers are transmitted at a time, eachtransmission layer comprising multiple beams. In one example,communicating 905 includes a UE receiving two transmission layers andfour beams, with N₁×N₂=16.

The method 900 includes identifying 910 a main beam for each of themultiple transmission layers and determining 915 whether the main beamsof each transmission layer are the same. As discussed above, theapparatus uses different codebook parameters based on whether the mainbeams of each transmission layer are the same.

The method 900 includes preparing 920 channel state information (“CSI”).Here, the CSI comprises a first bit indicating whether the main beams ofeach transmission layer are the same, a first set of bits coding themain beams, and a second set of bits coding the remaining beams. In someembodiments, the first set of bits coding the main beams includes onebit to indicate a main beam polarization for each transmission layer. Insome embodiments, the second set of bits coding the remaining beams usescombinatorial coding to indicate the remaining beams.

The method 900 includes transmitting 925 the CSI to the TRP. The method900 ends. In some embodiments, the CSI may be communicated by selectinga CSI codeword from a CSI codebook. In certain embodiments, the numberof transmission layers is two and the main beams are the same. Here, theCSI codeword may use enumerative coding to indicate a beam index of themain beam, in the first set of bits coding the main beam. In suchembodiments, the CSI codeword may further include one bit to indicatewhether the remaining beams all have non-zero wideband amplitudes. Whereat least one remaining beam has a wideband amplitude of zero, then thesecond set of bits coding the remaining beams includes a variable lengthcodeword to identify the at least one remaining beam having a widebandamplitude of zero.

In certain embodiments, the number of transmission layers is two and themain beams are not the same. Here, the CSI may use combinatorial codingto indicate a combination of beam indexes corresponding to the mainbeams of the two transmission layers, in the first set of bits codingthe main beams. In such embodiments, the second set of bits coding theremaining beams includes a variable length codeword with a specificprefix to indicate whether at least one of the remaining beams have awideband amplitude of zero. Moreover, the specific prefix may be atwo-bit value at the beginning of the variable length codeword, whereinthe remaining bits of the variable length code word are used to identifythe at least one remaining beam having a wideband amplitude of zero.Recall that the length of the specific prefix is based on the codingefficiency of the combinatorial code used to encode the remaining beams.For Condition-B (e.g., where the two main beams are not the same) withN₁×N₂=16 and L=4, the coding efficiency is 0.51 (using Equation 2) andthe prefix length is 2 (using Equation 1). In one embodiment, the secondset of bits coding the remaining beams uses range coding to combine theamplitude of each remaining beam having a non-zero wideband amplitudewith another CSI parameter.

The above described embodiments focus of the situation of N₁×N₂=16, L=4,and 2 transmission layers. However, the coding approach described hereinalso applies to other cases by coding the main beams, finding theefficiency of various combinatorial codes used for coding the remainingbeams, then adopting a variable length codeword based on the efficiencyof the combinatorial coding. In certain embodiments, inefficiently codedparameters may be combined to improve the coding efficiency. Moreover,range coding may be used with inefficient combinatorial codes to improvethe coding efficiency.

In one embodiment where the number of transmission layers exceeds two,the coding procedures described herein (e.g., coding the main beams,coding the remaining beams, etc.) is used for the first two transmissionlayers, while conventional coding techniques are used for the remainingtransmission layers. In another embodiment where the number transmissionlayers exceeds two, the coding procedures described herein (e.g., codingthe main beams, coding the remaining beams, etc.) is used for pairs oftransmission layers, with conventional coding techniques being used forany remaining transmission layers. In other embodiments, the codingprocedures described herein may be used to prepare a combined CSI, wherethe number transmission layers exceeds two.

FIG. 10 depicts a method 1000 for efficiently preparing CSI using zeroamplitude parameters, according to embodiments of the disclosure. Insome embodiments, the method 1000 is performed by an apparatus, such asthe remote unit 105, the UE 205, and/or the user equipment apparatus300. In certain embodiments, the method 1000 may be performed by aprocessor executing program code, for example, a microcontroller, amicroprocessor, a CPU, a GPU, an auxiliary processing unit, a FPGA, orthe like.

The method 1000 begins with communicating 1005 with a base unit over aradio access network using spatial multiplexing, wherein multipletransmission layers are transmitted at a time, each transmission layercomprising multiple beams.

The method 1000 includes identifying 1010 a set of non-zero amplitudeparameters over a set of layers. The method 1000 includes identifying1015 a set of zero amplitude parameters over the set of layers. Incertain embodiments, the amplitude parameters are represented by bits,integers, or values in a range. In certain embodiments, the amplitudeparameter is a beam amplitude.

The method 1000 includes computing 1020 a number of non-zero amplitudeparameters based on at least one of the set of non-zero amplitudeparameters and the set of zero amplitude parameters.

The method 1000 includes determining 1025 an indication of the number ofnon-zero amplitude parameters. In certain embodiments, determining 1025the indication of the number of non-zero amplitude parameters includescomputing a number of non-zero amplitude parameters based on the set ofnon-zero amplitude parameters and encoding the number of non-zeroamplitude parameters using a variable length code. In certainembodiments, determining 1025 the indication of the number of non-zeroamplitude parameters includes computing a number of zero amplitudeparameters based on the set of zero amplitude parameters and encodingthe computed number of zero amplitude parameters. Here, encoding thecomputed number of zero amplitude parameters may include encoding usinga variable length code.

The method 1000 includes determining 1030 the location of zero amplitudeparameters to generate a set of location bits. In some embodiments,determining 1030 the location of zero amplitude parameters to generatethe set of location bits includes generating the set of location bitsusing a combinatorial coding or an enumerative coding. In certainembodiments, generating the set of location bits comprises encoding thelocation of non-zero amplitude parameters using the combinatorial codingor the enumerative coding. In certain embodiments, generating the set oflocation bits includes generating the set of location bits comprisesencoding the location of zero amplitude parameters using thecombinatorial coding or the enumerative coding.

The method 1000 includes preparing 1035 channel state information(“CSI”), wherein the CSI comprises the indication of the number ofnon-zero amplitude parameters and the set of location bits. In certainembodiments, preparing 1035 the CSI includes preparing a combined CSIfor all of the multiple transmission layers. The method 1000 includestransmitting 1040 the CSI to the base unit. The method 1000 ends.

Embodiments may be practiced in other specific forms. The describedembodiments are to be considered in all respects only as illustrativeand not restrictive. The scope of the invention is, therefore, indicatedby the appended claims rather than by the foregoing description. Allchanges which come within the meaning and range of equivalency of theclaims are to be embraced within their scope.

The invention claimed is:
 1. An apparatus comprising: a transceiver that communicates with a base unit over a radio access network using spatial multiplexing, wherein multiple transmission layers are transmitted at a time, each transmission layer comprising multiple beams; and a processor that: identifies a set of non-zero amplitude parameters over a set of layers; identifies a set of zero amplitude parameters over the set of layers; computes a total number of non-zero amplitude parameters based on at least one of the set of non-zero amplitude parameters and the set of zero amplitude parameters; determines an indication of the total number of non-zero amplitude parameters, wherein the processor determines the indication of the total number of non-zero amplitude parameters by encoding the total number of non-zero amplitude parameters by selecting a codeword from a plurality of candidate codewords, wherein the length of at least one candidate codeword is not more than the number of bits needed to code the total number of non-zero amplitude parameters in binary; determines a location of zero amplitude parameters to generate a set of location bits; and prepares channel state information (“CSI”) wherein the CSI comprises the indication of the total number of non-zero amplitude parameters and the set of location bits, wherein the transceiver transmits the CSI to the base unit.
 2. The apparatus of claim 1, wherein the processor encodes the total number of non-zero amplitude parameters using a variable length code.
 3. The apparatus of claim 1, wherein determining the location of zero amplitude parameters to generate the set of location bits comprises generating the set of location bits using a combinatorial coding or an enumerative coding.
 4. The apparatus of claim 3, wherein the processor generates the set of location bits by encoding the location of zero amplitude parameters using the combinatorial coding or the enumerative coding.
 5. The apparatus of claim 3, wherein the processor generates the set of location bits by encoding the location of non-zero amplitude parameters using the combinatorial coding or the enumerative coding.
 6. The apparatus of claim 1, wherein the amplitude parameter is a beam amplitude.
 7. The apparatus of claim 1, wherein the amplitude parameters are represented by bits, integers, or values in a range.
 8. The apparatus of claim 1, wherein the processor determines the indication of the total number of non-zero amplitude parameters by computing a total number of zero amplitude parameters based on the set of zero amplitude parameters and encoding the total number of zero amplitude parameters.
 9. The apparatus of claim 8, wherein the processor encodes the total number of zero amplitude parameters using a variable length code.
 10. The apparatus of claim 1, wherein preparing the CSI comprises preparing a combined CSI for all of the multiple transmission layers.
 11. A method comprising: communicating with a base unit over a radio access network using spatial multiplexing, wherein multiple transmission layers are transmitted at a time, each transmission layer comprising multiple beams; identifying a set of non-zero amplitude parameters over a set of layers; identifying a set of zero amplitude parameters over the set of layers; computing a total number of non-zero amplitude parameters based on at least one of the set of non-zero amplitude parameters and the set of zero amplitude parameters; determining an indication of the total number of non-zero amplitude parameters, wherein determining the indication of the total number of non-zero amplitude parameters comprises encoding the total number of non-zero amplitude parameters by selecting a codeword from a plurality of candidate codewords, wherein the length of at least one candidate codeword is not more than the number of bits needed to code the total number of non-zero amplitude parameters in binary; determining a location of zero amplitude parameters to generate a set of location bits; preparing channel state information (“CSI”), wherein the CSI comprises the indication of the total number of non-zero amplitude parameters and the set of location bits; and transmitting the CSI to the base unit.
 12. The method of claim 11, wherein determining the indication of the total number of non-zero amplitude parameters comprises computing a total number of non-zero amplitude parameters based on the set of non-zero amplitude parameters and encoding the total number of non-zero amplitude parameters comprises encoding using a variable length code.
 13. The method of claim 11, wherein determining the location of zero amplitude parameters to generate the set of location bits comprises generating the set of location bits using a combinatorial coding or an enumerative coding.
 14. The method of claim 13, wherein determining the location of zero amplitude parameters to generate the set of location bits comprises encoding the location of non-zero amplitude parameters using the combinatorial coding or the enumerative coding.
 15. The method of claim 13, wherein determining the location of zero amplitude parameters to generate the set of location bits comprises encoding the location of zero amplitude parameters using the combinatorial coding or the enumerative coding.
 16. The method of claim 11, wherein the amplitude parameters are represented by bits, integers, or values in a range.
 17. The method of claim 11, wherein the amplitude parameter is a beam amplitude.
 18. The method of claim 11, wherein determining the indication of the total number of non-zero amplitude parameters comprises computing a total number of zero amplitude parameters based on the set of zero amplitude parameters and encoding the total number of zero amplitude parameters.
 19. The method of claim 18, wherein encoding the total number of zero amplitude parameters comprises encoding using a variable length code.
 20. The method of claim 11, wherein preparing the CSI comprises preparing a combined CSI for all of the multiple transmission layers. 